I don't see any cons to keeping pertinent information on hand. It will not stop anyone from asking questions. If someone needs a quick answer in the middle of the night, for instance, or someone simply wants to refresh themselves on some basics it would be a good idea.

Also, keep in mind that when we are starting out, there are basic aspects of betta care that we may not even realize we needed to ask about. The same valuable questions do not readily occur to everyone, a sticky could contain answers to questions people may not have thought to ask.